British and Chinese scientists have found a genetic variant which explains why Chinese populations may be more vulnerable to the H1N1 virus, commonly known as swine flu. The discovery of the variant could help doctors find those people at high risk of severe flu and prioritize them for treatment, researchers said. It may also help explain why new strains of flu virus often emerge first in Asia, where the variant known as rs12252-C is more common in the population than elsewhere, they said.